Restricting Microbial Exposure in Early Life Negates the Immune Benefits Associated with Gut Colonization in Environments of High Microbial Diversity

Imke E. Mulder, Bettina Schmidt, Marie Lewis, Margaret Delday, Christopher R. Stokes, Mick Bailey, Rustam Aminov, Bhupinder P. Gill, John R. Pluske, Claus-Dieter Mayer, Denise Kelly

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Background: Acquisition of the intestinal microbiota in early life corresponds with the development of the mucosal immune system. Recent work on caesarean-delivered infants revealed that early microbial composition is influenced by birthing method and environment. Furthermore, we have confirmed that early-life environment strongly influences both the adult gut microbiota and development of the gut immune system. Here, we address the impact of limiting microbial exposure after initial colonization on the development of adult gut immunity.Methodology/Principal Findings: Piglets were born in indoor or outdoor rearing units, allowing natural colonization in the immediate period after birth, prior to transfer to high-health status isolators. Strikingly, gut closure and morphological development were strongly affected by isolator-rearing, independent of indoor or outdoor origins of piglets. Isolator-reared animals showed extensive vacuolation and disorganization of the gut epithelium, inferring that normal gut closure requires maturation factors present in maternal milk. Although morphological maturation and gut closure were delayed in isolator-reared animals, these hard-wired events occurred later in development. Type I IFN, IL-22, IL-23 and Th17 pathways were increased in indoor-isolator compared to outdoor-isolator animals during early life, indicating greater immune activation in pigs originating from indoor environments reflecting differences in the early microbiota. This difference was less apparent later in development due to enhanced immune activation and convergence of the microbiota in all isolator-reared animals. This correlated with elevation of Type I IFN pathways in both groups, although T cell pathways were still more affected in indoor-reared animals.Conclusions/Significance: Environmental factors, in particular microbial exposure, influence expression of a large number of immune-related genes. However, the homeostatic effects of microbial colonization in outdoor environments require sustained microbial exposure throughout development. Gut development in high-hygiene environments negatively impacts on normal succession of the gut microbiota and promotes innate immune activation which may impair immune homeostasis.
Original languageEnglish
Article numbere28279
JournalP L o S One
Issue number12
Number of pages10
Publication statusPublished - 2011
Externally publishedYes


  • immune activation
  • indoor environment
  • maternal milk
  • microbial colonization
  • microbial diversity
  • microbial exposure
  • outdoor environment
  • Artiodactyla Mammalia Vertebrata Chordata Animalia (Animals, Artiodactyls, Chordates, Mammals, Nonhuman Vertebrates, Nonhuman Mammals, Vertebrates) - Suidae [85740] Sus scrofa species pig common immature female breed-Large White, breed-Landrace
  • Microorganisms (Microorganisms) - Microorganisms [01000] microbiota common
  • immune-related genes expression
  • interleukin-22 IL-22 signaling
  • interleukin-23 IL-23 signaling
  • Th-17 signaling
  • type I interferon type I IFN signaling
  • 03502, Genetics - General
  • 03506, Genetics - Animal
  • 14004, Digestive system - Physiology and biochemistry
  • 34502, Immunology - General and methods
  • Biochemistry and Molecular Biophysics
  • Chemical Coordination and Homeostasis
  • Ingestion and Assimilation
  • gut digestive system
  • gut epithelium digestive system
  • Digestive System
  • Immune System
  • Molecular Genetics


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